1. Field
The aspects of the disclosed embodiment refer to storage stacks for a modular sample store for storing biological, chemical and/or biochemical samples. More particularly, this application refers to storage stacks comprising particular insulation covers for use in a temperature controlled modular sample store for storing such samples at controlled temperature conditions, preferably in the range of −25° C. to −90° C. In the preferred embodiment, this application refers to a storage stack for storing sample containers in a low temperature sample store. Such a low temperature sample store is equipped with a robot that is capable to acting according to Cartesian X, Y, and Z coordinates for horizontally positioning sample containers in X/Y planes inside of individual storage stacks. The robot is also capable to vertically moving individual storage stacks within the low temperature sample store in Z direction between a bottom storage position and elevated access positions. The sample store typically defines a storage area for accommodating an array of such storage stacks. This storage area preferably comprises a number of first lattice constants of an orthogonal lattice in the horizontal X direction and a number of second lattice constants of said orthogonal lattice in the horizontal Y direction. The total number of storage stacks of the storage stack array is accomplished to be oriented adjacent to each other and parallel to the vertical Z direction.
2. Brief Description of Related Developments
Biological samples, such as body fluids (e.g. blood, urine, sputum or sperm), cells (e.g. bacterial cell cultures), or tissue samples (e.g. taken from human, animals or plants) are extremely temperature sensitive and have to be cooled or frozen immediately after taking the samples in order to prevent their destruction. Thus, an important aspect during investigation of biological samples and temperature sensitive samples in general is storage and provision of these samples in frozen state, i.e. at low temperatures. Storage and provision can be done in commercially available freezers (i.e. at temperatures of at most −18° C.), in a gas atmosphere that is cooled by dry ice (i.e. solid C02) to −78.5° C., or in liquid nitrogen (at −196° C.). In addition, freezers operating with compressors are known which provide storage temperatures of −35° C. (single-stage), −85° C. (double-stage), or −135° C. (triple-stage).
All these storage procedures and apparatuses are well known, but also provide certain drawbacks. Samples stored at a temperature of −18° C. can exhibit destruction artifacts already after short storage terms because of growing ice crystals. Such ice crystal growth is considerably reduced at dry ice temperatures and essentially does not take place in liquid nitrogen. However on the one hand, dry ice cooled containers warm up relatively fast as soon as all of the C02 has sublimated. On the other hand, storage in liquid nitrogen is cumbersome and only possible with dedicated safety measures and appropriately educated personal. Especially for robotic or automated storage and withdrawal/provision of a large number of samples there exist only very few of the known systems. Chemical samples (e.g. prepared reagent aliquots of defined concentration) and biochemical samples (e.g. concentrated and purified enzymes) are known to be stored more and more in automatic storage systems for large laboratories with the task of being provided and accessible at any time. In so called “large stores” or “bio-banks”, storage temperatures of about −20° C. for chemical samples and of about −80° C. for biological and biochemical samples have proven to be reasonable.
From the U.S. Pat. No. 6,357,983 B1, an automatic storage system is known. In a conditioned chamber, the temperature of which being selectable in a range from −20° C. to +20° C., there are located two ring-like, nested shelves, which are rotatable around a common central axis, and which comprise a large number of horizontally orientated, superimposed shelf board positions. These shelf board positions can be accessed by a robot that moves vertically and outside of the shelves. This robot is equipped with an especially articulated gripper mechanism in order to reach to an inner shelf board position by penetrating an adjacent outer shelf board position. This system has the advantage that the robot, and thereby the sample, are located within the cold atmosphere during the entire process of selecting the sample. However, this system seems to be rather limited in the number of shelf boards, which results in cooling down a relatively large volume that can take up only a quite small number of samples. Moreover, a rather complex robot mechanism has to be utilized.
Another storage system for storing and providing frozen samples is known from the patent application EP 1 939 561 A2. This document discloses a compact storage system and a related method for storing frozen samples in such a compact storage system, which comprises a storage area within a thermally insulated housing that is equipped with a cooling device for cooling the storage area to at least −15° C. This compact storage system comprises revolving storage shelves in the form of a paternoster that are arranged entirely within the cooled storage area. This compact storage system also comprises a transfer area that is located above said storage area, a robot being moveable in essentially horizontal directions within this transfer area. The robot is accomplished to load a storage shelf into or to remove a storage shelf from the uppermost position of the upper half circle of the revolving storage shelves. The robot can also take out from a storage shelf or insert a single object into a storage shelf that is located at this vertex position of the paternoster. The storage area of this system appears to be quite compact. However, the mechanics of the paternoster have to be moved at temperatures down to −80° C.; because of the danger of frost condensation and thereby blocking the mechanics of the paternoster, elaborate and expensive measures are believed to be essential.
Other storage systems of the company REMP AG (Oberdiessbach, Switzerland) are known, in which samples are stored at +4° C. or −20° C. (REMP Small-Size Store™), or in which samples are stored at −80° C. (REMP Bio-Sample Store). In the latter, a robot is implemented that is fully operable at −20° C.
Again another storage system is known from the patent U.S. Pat. No. 6,694,767 B2. Below a working area with controlled atmosphere, in which a robot with workplace is arranged, is located a thermally completely insulated storage space that is accomplished for storage temperatures of −85° C. to −80° C. Storage shelves with relatively small horizontal dimensions and numerous shelf boards superimposed to each other are vertically suspended in openings of the thermally insulating ceiling plate of the storage area. The storage shelves comprise an upper cover, that carries the storage shelf and that overlaps and closes the opening in the thermally insulating ceiling plate in which the storage shelve is completely inserted. Such closing of the access opening for inserting a storage shelf is always carried out under the effect of gravity, i.e. in their down-most storage position, the storage shelves actually hang with their upper cover at the thermally insulating ceiling plate. A robot lifts such a storage shelf out of the storage area in order to allow accessing a particular shelf board by an appropriate tool for removing a sample container from that shelf board of for depositing a sample container on that shelf board.